2004 Ram 1500 4.7 with 48k miles. So about 3 weeks ago it started taking longer for it to start in mornings and whenever it set for a little bit. By that i mean it will crank like a champ but not fire for about 5 seconds. Always starts on second try. Okay so i am thinking the check valve or fuel pump is going bad and letting fuel pressure drain off. Well, thats in the tank so i am going to start with simple things before i get to that. Sooo, changed the plugs. Seemed to help for about 3 days. Then back to the normal routine if not worse. Okay, got me a can of seafoam and did the ole vaccum line trick. Couldn't get it to die out but was close enough. Let it set overnight with the seafoam inside of it. Next morning, you guessed it what a show. So as i am driving it like i stole it for about 30 minutes i notice this miss and a stutter at takeoff. It also feels like it might be idling just a tad bit low. Anyways i thought well you know what it is just the seafoam still inside. Well after that i parked it for little bit. Went back out and got into it and drove around for about another 20 minutes, still had the miss and stutter. Okay well then i get into it 2 hours later and i get the dreaded CEL. Okay so i do the key trick and it gives me P0307. Okay so #7 is not firing. Pull the plug, now remember they are about 2 weeks old. No problems there, so i put it back in and leave the wire off of the coil pack. No difference whatsoever in the idle. Still have a miss to it. So, to verify it is coil pack i swap with number 6. Well, it still has the exact same missfire and stutter but i cannot get a code to pop up. So here is my question, go buy a new coil pack, plugs or is it something i am not thinking of. Any and all help is appreciated.

 

if you swapped coil packs and spark plugs and it still doesn't fire on the same cylinder it wouldn't be the coil pack or the spark plugs..............maybe when you changed the plugs for the new ones you accudentily pulled a wire loose from that specific coil pack or broke a wire a little bit.i'd check the wire to the coil pack as far as i could first

 

Could also be a bad plug. I know they are like new but in todays age of techno anything is possible and ive had new plugs be bad right off the bat. When i doubt swap it out. Good luck

 

thanks for the help. It ended up being the spark plug, but the trick was that it would only do it when it got hot. In another words, when you ohm'd it out when it was cold it was fine, but once it heated up was when it was messing up. Oh, well, now i have a extra coil pack.